Mechanical hammer



June 11, 1946. LE, ATT 2,401,794

MECHANICAL HAMMER Filed Oct. 21, @945 20 L9 15 '14 5/ l6 I5 17 I Ryan/or ZawrerzceEPra 27 y ;H l W%4e44,@&am I zs LL Y j e/ fy Patented June11, 1946 UNITED STATES PATENT F F ICE MECHANICAL HAMMER Lawrence E.Pratt, Chicago, 111. Application October 21, 1943, Scri'al No; 507,112

2 Claims.

My invention relates to what may be termed a-mechanical hammer in thesense that ittakes the place of a hammer in the hand to deliver hammerblows on a tool such as a Starr drill,

for instance, which is being held in the other hand,

This has'been accomplished in part by taking any convenientl drivenrotary motion, such as an electric drill or flexible shaft having athrust bearing of its own, and converting it into I a reciprocatingmotion. While the invention is shown and described asoperating a Starrdrill by means of an electric drill, it is possible, with proper chucksand attachments, to use it in many places where-pneumatic tools are nowused, such 'as chiseling, riveting, hammering, etc.

It is an object of 'my invention to provide a tool of the classdescribed which shall be capable of being slipped into the chuck of anelectric drill, for instance, and 'used therewith with-substantially thesame facility as any tool, which shall be simple, easy and economical ofmanufacture, rugged, and of few parts, which carries the Starr drill orother tool by'a'special chuck, and which converts the rotary motion ofthe electric drill into a reciprocating motion of the Starr drill or itschuck.

Further objects and advantages will appear from the detailed descriptionand claims to follow, in connection with the accompanying drawing whichillustrates an-embodiment of m invention, and in which Figure 1 is alongitudinal central section through the device, parts being shown infull;

Fig. 2 is an exploded view of the motion converting means, the elementsbeing shown in perspective;

Fig. 3 is an end elevational'view of the chuck end'of the device;

Fig. 4 is a section through the meeting paths of the cam balls, showingthe slightly different radial distances of the balls in the two membersfrom the axial line of the tool, and also showing the center punching ofthe cages to prevent the balls from falling out; and

Fig. 5 is'a perspective'view of a cylindrical cam member which may beused instead of balls.

Referring to the drawing, the chuck III of a port-able hand'electricdrill is-indicated in dotted lines in Fig. 1. Such drills are driven bsmall electric motors, have their own thrust bearings and arehand-manipulated. The motor, of course, rapidly rotates the chuck Ill.

The mechanical hammer comprises the driving shaft ll, seen also inperspective in Fig. 2, the upper end of which is reduced in diameter andI fits securely within the chuck II] of theelectric drill.

On'the opposite endof this driving shaft u is fitted a backingdisc I2and a cage disc I3, the

latter being threaded on the reduced end of shaft II and clamping thebacking disc I2 against the shoulder-on shaft ll. Thus the shaft II andthe two'discs I2 and I3 are'allrigidlysecured and rotate together. 7 Thebacking plate or disc I2, as also the cage I3, should lie'accurately'in'planes at right angles or perpendicular to the axis of shaft H.

The cage disc I3, so called, accommodates, in suitable aperturestherethrough, two balls I4. These balls are slightly greater in diameterthan the thickness of the cage disc It, the projecting portionsconstituting cam surfaces adapted in their rotation to strike and camover corresponding balls in the opposing member, For this reason thereare preferably two such balls I4 diametrically opposite -and equallydistant from the axis in the driven member, so that a balancedoperation-may be had.

This driving cage disc member l3 faces a similarly constructednonrotatable driven member consisting of protruding balls I5,-six innumber, diametrically opposite in pairs, in perforations in the cagedisc It, which is not quite as thick as the diameter of theballs, andwhich is backed by the plain backing 'clisc IT. This disc I! in thedriven member and the disc l2 in the driving member receive thelongitudinal thrusts of the balls I l and I5 as they strike each otherin the revolution of the driving member. These two cage discs I3 and Itshould be the same thickness to-get the full throwof the driven member.If one is-less, the stroke is reduced to that extent.

These discs It "and H are mounted on the threaded endof hammer memberI8, on the inside of the housing member IS, the end of the latter lyingagainst a leather or similar gasket 19a on th'eflange Hla on member I8,and the cage disc is, with its flat sides'IBa for the reception of asuitable tool or wrench, threading on the end of member I8, clamps allthese relatively stationary parts, It, I1, "I8 and [9, together. Thecage Iii and *backpla'te 11 should be perpendicular to the aidsorcente'r line'of'the shaft I8 and thisshould be in-align'ment with theaxis of shaft the driving discs. At its open end it receives thethreaded bearing plug 20, having a flange at its outer end whichbindingly engages against the gasket Zia. of leather or other suitablematerial on the edge of housing i9. Spanner wrench sockets in the top ofplug 2G enable the same to be turned by a suitable wrench.

This bearing plug 20 has a bushing 2| in two end parts forming a bearingfor the rotatable shalt H and having a convenient oil seal 22. Bypushing the ends of bushings 2| closer together the oil seal becomesadjusted to the shaft II. This bushing 2| is preferably formed ofself-lubricating material. In practice, a small amount of lightlubricating oil is preferably sealed within the housing [9, the gasketsI90, and 2la and the oil seal 22 preventing any escape thereof or theentrance of any dirt. p

The threaded shank of the hammer member I8 receives the tool chuck 23which is finally secured in position on the stem by the lock nut 24tightened against it either directly, if no auxiliary handle is used, orthrough the same, if used.

4 and the stationary set of balls are brought into the path of therotating balls, with the result that the balls act as cams, and sincethe driven end is held from rotation it vibrates or reciprocateslongitudinally as the rotating pair of balls 14 strike the nonrotatingpairs of balls I 5. This has the effect of rapidly hammering on thedrill to cause it to do its work. Such drills are used in stone,plaster, and the like, and are supposed to be turned 90 or sointermittently. That is accomplished here by turningthe housing back andforth while held in the hand. If desired, the

housing 19 may bealternately released and In the present. instance thechuck 23 is a Starr,

drill chuck, having a central bore. The Starr drill 25, which isoctagonal in cross-section, When inserted in the chuck 23 abuts the endof the hammer-shank I8. The drill 25 is indicated in broken lines inFig. 1.

A'locking plate or jaw 26 at the end of the chuck grips the drill byfriction by tilting slightly. The drill can be easily and quicklyremoved or inserted by pressing the jaw or plate 26 against the end ofthe chuck and sliding the drill 25 into or out of place. The aperture inthe jaw 26 is octagonal to fit the drill. Since there are difierentsizes Of such Starr drills, different chucks 23 device several chucks ofdifferent sizes go with the device.

The hinge point of this plate 26 is on pin 21 which is secured in thechuck. The aperture for :should also be provided and in the sale of thegripped in the hand, thus permitting the housing to turn intermittentlyand the Starr drill properly to do its work.

While the ball I4 and I5 may be the same distance from the axial line ofthe driving and driven members, for a freer action one radius may be afew thousandths Of an inch greater than the other. Thus, as indicated bythe arrows in Fig. 4, the radius of one may be slightly shorter" thanthat of the other, so that the balls Will contact each other ofi centerand willrevolve in their cages, thus permitting afreer passing of theballs over each, other.

This arrangement also tends to keep the parts centered and the drivingand driven members in axial alignment in operation, keeps the bearing 2|from wearing out of line and prevents any tendency of the end of shaft Hto Whip, and if Wearing does take place the balls still strike squarely.I

As before stated, the number of balls in the driving and driven membersmay be varied, though I prefer the arrangement shown. The number of theballs in the driven member depends largely upon the size of the ballsand the inside diameter of the housing and the number thepin 2! in thelock plate is suitably reamed or bevelled out on both sides of theplate, as

indicated in Fig. 1, to permit the plate freely to hinge back and forth.At the opposite edge of the disc or plate 26, two spaced pins 28 pass athrough slots, shown dotted in Fig. 3, in the disc 25 and are secured inthe chuck end. A coil spring 28a is located in a hole or bore in thechuck between the pin 28 and bears outwardly on the inside of the disc26, as shown.

In the position shown, the edges of the aperture through which the drillpasses grip and tend to bite into the drill and so look and prevent itfrom coming out of the chuck. At the same time it is quickly freed fromthe disc by pressing the disc against the chuck.

The stationary or nonrotatable part of the device, to Wit, the drivenmember, is normally and preferably held in one hand when the device isin use, and is thus prevented from turning; but some might prefer theoptional handle 29 in the form of a ball connected by a strip or rod ofmetal with a loop 30 passing around shank l8 and clamped in positionbetween the lock nut 24 and the end of chuck 23.

In operation, it is usual to hold the electric can It in one hand andthe housing H) in the other. There is a sufficient clearance between theinner end of the plug bearing 20 and the adjacent backing plate I2 topermit the driving and driven ball members to be entirely separated and.out

- of contact. But by placing the Starrdrill against of reciprocationsper minute of the tool that is deemed best adapted to the work. It issimple to change from one to another by removing the bearing plug 20 andthe driving assembly as a unit; then unscrewing the case 16 by thespecial wrench engaging the flattened sides 16a. and removing same andits balls; then replace the cage and balls by another disc and balls ofa different number of pairs and reset plug 20. Other changes andsubstitutions of balls may be made in this simple way.

The ball cage openings in both cages l3 and It may be upset on the facesurfaces by any convenient method, such as center punching 3|, out ofthe path of 'travel of the balls, to provide a means of holding theballs in their cages. This,

. of course, should be done before the discs are hardened.

All parts should be made .of' proper material and hardened, if need be,for proper operation of the unit. By having the backing discs I2 and I Iand the cages l3 and it harder than the balls, most of the wear will beon the balls, which readily may be replaced with commercial bearingballs of proper size.

Fig. 5 shows short cylinders orrollers 32 with rounded ends which may beused instead of the balls in the cages l3 and 16. The rounded ends, ofcourse, would protrude and form the cams to convert the rotary drivingmotion into the reciprocating driven motion. Opposing stationary cams inplace of the balls or rollers could be used, or balls or cylinders couldbe used in one member while a fixed cam or cams were used in the other.

ferred.

The design and mode of operation of this unit are such that the threadedparts will automatically stay firmly attached to their respective parts.

It is apparent from the foregoing that I have produced an extremelysimple and effective device for the purposesintended, that it iscomparatively inexpensive to manufacture and maintain and is of longlife, that it is readily disassembled for inspection, care and repair,and that the parts most likely to wear and need replacement arestandard, commercial, readily procurable parts, such as balls used forball bearings.

Utilizing the thrust bearing of the electric drill dispenses with thenecessity of one in this device. The device is close-coupled. Thebacking plates and cages are all in planes parallel to each other and atright angles to the center line of the driving and driven members, whichgives accurate action. The whole unit is compact, small, light in weightand easy to handle. It can be handled like the drill; that is, anelectric drill with this device in its chuck is handled substantiallythe same as the drill without it. It is easily carried in the operatorskit of tools, and increases the usefulness of the electric drill. Itslabor-saving feature and ease of operation over the old hand hammer andStarr drill method are apparent.

The chuck is simple, easy to operate, provides quick change in case ofsharpening drill or for other purposes.

Having thus described my invention and the best manner known to me ofcarrying same into effect, and appreciating that various changes andalterations may be made therein without departing from the spirit of theinvention or the intended scope of the claims to follow, what I claimand desire to secure by Letters Patent is:

l. A device of the class described adapted to be received and connectedas a tool in the chuck of a hand-manipulated, electric or power drillstock, comprising a cylindrical housing, opposed discs therein,interengaging camming balls locked in the opposed faces of said discs,one of said discs being rigidly secured in one end of the housing, atool chuck secured to the outside of that end of the housing and adaptedto receive a percussion drill therein, a driving shaft connected withthe other disc, a bearing therefor in the opposite end of the housing,said shaft being rotatable and reciprocable in said bearing andadapted-to be received at its outer end in the chuck of thehand-manipulated drill stock, whereby when the drill is pressed againstthe work the discs approach each other and the balls are brought intocamming engagement and deliver hammer-like blows on the drill and whenthe pressure is relieved on the drill the balls force the discs apartwith the balls out of striking engagement with each other.

2. A power mechanism for converting rotary motion into reciprocatorymotion comprising in combination a member rotatable by a source ofrotary motion and a second member adapted for reciprocatory motion, aframework for supporting both said members, said first member includingat least one pair of spheroidal cam elements, the elements of the pairbeing diametrically opposed with respect to the axis of rotation andequidistant therefrom, said second member including at least one pair ofspheroidal cam elements, the elements of that pair being diametricallyopposed with respect to said axis and equidistant therefrom, theelements of both pairs being in opposed relation and adapted uponrotation of said first member for camming relation therebetween, and theradial distance of the center of the spheres forming one pair ofelements from said axis being greater than the radial distance of theopposed pair whereby the successive points of contact of the elementsduring rotation lie on a circle whose radius is intermediate said othertwo radii.

LAWRENCE E. PRATT.

